The present invention relates to non-contact communication systems provided with an interrogator and a responsor generating power from a radio frequency signal transmitted from the interrogator and transmitting, to the interrogator, information as a response to information obtained from a modified signal received from the interrogator, and interrogators used in the same.
Conventionally a radio frequency (RF) tag which obtains power from electronic waves transmitted from an antenna to transmit information internally stored has been devised and used in operation e.g. of ski lifts, train ticket gates, freight sorting, and the like. The RF tag is provided in the form of a non-contact card which has a non-volatile memory and an information transmitting and receiving scheme and is not provided with power supply, such as a battery. The non-contact card obtains power to consume from a received electronic wave (a radio frequency signal). Thus the card is not required to incorporate a battery therein and is thus capable of long-term exchange of information. The non-contact card also communicates information via electronic waves and is thus capable of non-contact communication of information.
At present in such a non-contact communication system there are two systems, i.e., signal superimposition system and signal separation system. Signal superimposition system provides data (information) communication and the power-supply to a non-contact card via a signal having a single frequency and thus only requires a single antenna at least for the non-contact card. By contrast, signal separation system provides data communication and power supply via signals having different frequencies and thus requires two antennas for a non-contact card. In addition to such different systems as signal superimposition system and signal separation system, there are various modulation systems, such as amplitude modulation, phase modulation. Thus between communication systems having different systems their respective non-contact cards or interrogators cannot be used mutually.
The present invention contemplates an interrogator capable of accommodating both of signal superimposition system and signal separation system, and a non-contact communication system including the interrogator.
One object of the present invention is achieved by providing an interrogator transmitting interrogation data to a responsor converting a received electronic wave into power and receiving response data from the responsor, including a first modulation circuit modulating according to interrogation data a first signal having a first frequency, a first transmission circuit transmitting to the responsor a signal modulated by the first modulation circuit, a second modulation circuit modulating according to interrogation data a second signal having a second frequency, a second transmission circuit transmitting to the responsor a signal modulated by the second modulation circuit, a reception circuit receiving a signal modulated by the responsor according to response data, and a select circuit selectively activating any one of the first and second modulation circuits in response to a signal received at the reception circuit.
An object of the present invention in another aspect is achieved by providing an interrogator including a first transmission circuit transmitting a first signal having a first frequency for supplying power and interrogation gate to a responsor, a second transmission circuit transmitting to the responsor a second signal having the first frequency for supplying power to the responsor and a third signal having a second frequency and modulated according to interrogation data, and a select circuit selectively activating any one of the first and second transmission circuits according to response data transmitted from the responsor.
An object of the present invention in still another aspect is achieved by providing a non-contact communication system provided with an interrogator and a responsor receiving an electronic wave transmitted from the interrogator to generate power and transmitting, to the interrogator, response data to data transmitted from the interrogator, the interrogator including a first transmission circuit transmitting a first signal having a first frequency for supplying power and data to the responsor, a second transmission circuit transmitting a second signal having the first frequency for supplying power to the responsor and a third signal having a second frequency for supplying data to the responsor, and a select circuit selectively activating any one of the first and second transmission circuits according to response data transmitted from the responsor.
Thus the present invention can advantageously provide an interrogator capable of communicating information and a non-contact communication system including the interrogator, whether the system adopted by a responsor is signal superimposition system or signal separation system.